A man rides his bicycle today past the scene of an explosion at a police headquarters building that killed at least a dozen people, wounded more than 100, and left scores buried under the rubble, in the Nile Delta city of Mansoura, 70 miles north of Cairo. The country's interim government accused the Muslim Brotherhood of orchestrating the attack, branding it a "terrorist organization."

Mostafa el-Shemy / AP

View photo

Cairo

Egypt’s prime minister declared the Muslim Brotherhood a "terrorist" organization after multiple explosions at the security headquarters in the Nile Delta city of Mansoura killed at least 12 and injured more than 100.(Editor's note: This sentence was revised to clarify the government's position.)

Although militants with no connection to the Brotherhood are believed to be behind the attack, the organization is suffering the aftereffects. Cabinet spokesman Sherif Shawki blamed the Brotherhood, saying it has revealed its “ugly face as a terrorist organization shedding blood and messing with Egypt’s security,” according to the state-run Middle East News Agency.

Egypt’s interim government has led an extensive crackdown against the Brotherhood and other supporters of Mr. Morsi, killing hundreds and arresting thousands more. The movement, which sat at the apex of Egypt’s political establishment only five months ago, has repeatedly been described by officials as a new enemy in the military’s self-described "war on terrorism."

Officials have accused the the group of having links to a wave of jihadist attacks across the country since former president Mohamed Morsi was ousted in a military-led takeover, often launched by an amorphous network of groups based in the country’s volatile North Sinai region. To date, no connections between the Brotherhood and militants have been proven. The attack in Mansoura is the latest, and deadliest, in the campaign.

Two near-simultaneous blasts occurred inside the city's security directorate compound shortly after 1 a.m. Security officials say that a third set of munitions, concealed inside a car, was later defused. Images of the partially collapsed building were plastered across state television, which interrupted its late-night programming to urge viewers to donate blood for the casualties at local hospitals.

Most of the fatalities are believed to be policemen, many crushed below the debris of the collapsed building. Two of Mansoura's top security officials, Maj. Gen. Samy al-Mehy and Brigadier Said Emara, are among the wounded, Reuters reported.

Although no one has claimed responsibility for the Mansoura attack, key suspects will include Ansar Bayt al-Maqdis, an Al Qaeda-linked group which has claimed responsibility for a number of attacks on Egyptian urban centers, including the attempted assassination of interior minister Mohamed Ibrahim in October. Since Morsi's ouster on July 3, there have been more than 260 attacks in the Sinai peninsula, most targeting Egyptian security forces and assets.

The attack comes a day after Ansar Bayt al-Maqdis called on members of Egypt’s security forces to repent and leave their positions. Those who remain in service will have no one "to blame but himself,” it said in a statement posted on jihadist forums. "[W]e are the most resolute and determined to carry out the command of Allah and His Messenger to do jihad against you and fight you until all the religion is for Allah."

“It is certainly possible this was a follow-up to the Ansar Bayt al Maqdis threat to target those who do not leave the security services,” says David Barnett, research associate at the Foundation for Defense of Democracies, and an expert on jihadist movements.

“We will only know for certain if they claim responsibility, however. Ansar Bayt al Maqdis has said on a number of occasions that it seeks to target police and military headquarters, and unfortunately, they have kept their word more than once.”

The Muslim Brotherhood’s London press office issued a swift denial of alleged links to Tuesday's attack, saying it considered the bombing “a direct attack on the unity of the Egyptian people and demands an enquiry forthwith so that the perpetrators of this crime may be brought to justice.”

“It is no surprise that Beblawi, the military junta's puppet Prime Minister, has decided to exploit the blood of innocent Egyptians through inflammatory statements designed to create further violence, chaos and instability,” it said in a statement e-mailed to journalists.

But in a political climate already characterized by deep mistrust of the Brotherhood, such denials are unlikely to gain much traction. According to a recent poll by Zogby Analytics, two-thirds of the population mistrusts the embattled Islamist movement. Official designation as a terrorist movement would undoubtedly exacerbate fear and mistrust.

Among government opponents, there will be fear that Tuesday's attack may be used as a justification to extend the reach of its crackdown. On Monday, three leading instigators of Egypt's 2011 uprising were jailed for three years, charged with organizing "illegal protests."